Comments

I’m used to consult Flora Agaricina Neerlandica, Vol. 6, to classify coprinoid mushroom. However, this time none of the two candidate species – Coprinopsis marcescibilis (var. virginea) and Coprinopsis lotinae appears there; The first was transfered from Psathyrella and the second appears after its publication. Therefore, I used the website of Andreas Melzer to reach the classification:http://www.vielepilze.de/coprinus/coprinus.html
Let me also say that some authors take these two species as synonyms and as far as I can see, from these specimens, maybe it would be the best option. The question can be summarized more or less as follows, regarding the microstructures, since the macrofeatures are clearly very similar as can be seen from the photos at the website reffered above:

- Both species have 4-spored basidia, but C. marcescibilis can also have some 2-spored;

- Both species have similar sized cheilocystidia, but with different forms: C. marcescibilis – usually subapical constricted to significantly capitate, sometimes forked, and mixed with a few sphaeropedunculate and clavate marginal cells; C. lotinae – utriform;

- Both species lack pleurocystidia and, in fact, I didn’t observe any;

- Both species have caulocystidia, but with different size and forms: C. marcescibilis – 24.5 to 60 (-70) x 7-22 um, often, usually apically swollen in large bunches, mingled with a few clavate cells, from 16.5 to 35.5 × 7 to 16.5 um; C. lotinae – 66-87 × 18-30 um, utriform, clavate;

Summarizing, many points in favor of C. marcescibilis (existence of 2-spored basidia, existence of sphaeropedunculate and clavate marginal cells at the gill edge) and maybe the point against is the form of caulocystidia; the size of caulocystidia, is also not in favor of C. lotinae, since this species has more uniform and bigger ones. The spores, and mainly the value of Q, is clearly a point in favor of C. lotinae.

I’m facing problems with my microscope, which didn’t permit to continue the microscopy of these specimens. I could only observe the spores, whose dimensions are very promising towards Psathyrella marcescibilis var. virginea, according to the website of Andreas Melzer, where this species in included in the genus Coprinopsis (Subsect. Marcescibili).
It should also be mentioned that some authors consider this species as a synonym of Coprinopsis lotinae as one can see in the topic devoted to this species in the “A.M.B Forum di Micologia” (see the link below), where several photos illustrating specimens similar to mine are given and an extensive treatment of the microscopic characters is presented.
Whenever possible I intend to go back to the microscopy.